1. Field of the Invention
The present invention relates to a magneto-optical disk device.
2. Description of the Prior Art
Magneto-optical disk devices such as are conventionally known are shown in FIG. 1 and FIG. 2.
The magneto-optical disk device shown in FIG. 1 is a device in which the magnetic field coil 22 which applies a magnetic field to one side of the magneto-optical disk 21 is integrated with an optical head 23 which irradiates the other side of the magneto-optical disk 21 by means of a laser emission port 24. This integrated assembly slides parallel to the surface of the magneto-optical disk in the directions indicated by the arrows. The magnetic field coil 22 and laser emission port 24 sandwich the magneto-optical disk 21 from mutually opposing positions so that a magnetic field is applied by the magnetic field coil 22 to that part of the magneto-optical disk irradiated by the laser.
The magneto-optical disk device shown in FIG. 2 is a device in which the magnetic field coil 32 is mounted to, for example, a cassette holder (not shown in the figure) for the magneto-optical disk 31, and is of a size large enough to apply a magnetic field to the entire media area of the magneto-optical disk. The optical head 33 slides, as does the optical head in the device shown in FIG. 1, parallel to the surface of the disk such that laser light from the laser emissions port 34 irradiates the magneto-optical disk 31.
However, because the magneto-optical disk is typically of a cassette type, sufficient space is required in a direction perpendicular to the magneto-optical disk surface in order to load the disk. Thus, in a magneto-optical disk device as shown in FIG. 1, space for cassette loading is required between magnetic field coil 22 and the magneto-optical disk 21, and between laser emission port 24 and the magneto-optical disk 21. Thus, with such a spacing, magnetic field coil 22 cannot be positioned any closer than a fixed distance from the magneto-optical disk. Therefore, the magnetic field coil must be of a size sufficiently large to apply, from this fixed position, a magnetic field of the required strength to magneto-optical disk 21. Thus, this magnetic field coil cannot be made smaller and the weight cannot be further reduced, and the access speed of the optical head therefore becomes slower.
Furthermore, as to the arrangement of FIG. 2, because the magnetic field coil 32 is mounted to the cassette holder and moves in conjunction with the cassette during cassette loading, extra cassette loading space between the magnetic field coil 32 and magneto-optical disk is not required in a magneto-optical disk device, but the magnetic field coil 32 must be of a size sufficient to apply a magnetic field to the entire media area of the magneto-optical disk. Thus, the current flowing through the coil is greater, the amount of heat created is greater, and the power consumption is greater.